Numerous previous studies have been occupied with the biological function of S-IgA and with the deleterious consequences of primary IgA deficiency. A large number of clinical problems may, however, be related to a secondary defect of mucosal immunity due to toxic agents, acute or chronic infections. Any agent which interferes with the synthesis of secretory component (SC) may hypothetically render mucosal surfaces devoid of the S-IgA "antiseptic paint". The overall goal of the present study is to evaluate the interferences in the assembly and secretion of S-IgA by viruses, employing several established in vivo and in vitro animal models. Normal and IgA and T cell deficient rabbits will be used. Respiratory viruses and temperature sensitive mutants of adenovirus will be instillated into rabbit trachea, tracheal epithelium in culture, tracheal pouch or cultured type II alveolar cells. Infected tissues or cells will be studied to detemine SC synthesis and S-IgA assembly and secretion, employing immunohistochemical techniques, immunoprecipitation and gel electrophoresis.